# Multivariate dynamic association analysis between sprint interval training and adolescent freestyle swimming performance

PMID: 41555447
Journal: BMC Sports Science, Medicine and Rehabilitation
Published: 2026-01-19
Authors: Chen X, Jiang Y, Shen Y

## Question

Can complex network modeling describe the dynamic multivariate associations between a single 6 x 50 m sprint interval swimming session and 100 m freestyle performance in adolescent swimmers?

## Summary

This cross-sectional sports science study tested 16 highly trained adolescent swimmers during a single 6 x 50 m maximal freestyle sprint interval session and a separate 100 m freestyle time trial. The researchers measured swimming velocity, stroke rate, stroke length, blood lactate, and RPE, then used complex network modeling to examine how these variables related to 100 m freestyle performance across the six sprint repetitions. Network structure stayed relatively stable, while velocity, lactate, and RPE became more central as fatigue accumulated; stroke rate became less central and stroke length stayed comparatively stable.

## Population

- Sixteen highly trained adolescent freestyle swimmers with at least five years of formal swim training.
- Sample size: 16
- Age: Males 15.89 +/- 1.05 years; females 16.29 +/- 0.76 years
- Sex: 9 male, 7 female
- Fitness level: Highly trained swimmers; Tier 3 by McKay classification; high-intensity swimming at least twice weekly and about 16 h/week total training
- Health status: Good physical and mental health; no cardiopulmonary disease or musculoskeletal injury in the preceding year

## Methodology

- Cross-sectional, exploratory complex network modeling study of one sprint interval session and one 100 m freestyle time trial.
- Single-session SSIT test plus separate 100 m freestyle test separated by 48 hours
- Standard 50 m indoor swimming pool with water temperature 26-28 degrees C and relative humidity 40%-60%.

## Protocol

- 6 x 50 m SSIT.
- Modality: Freestyle swimming.
- Work intervals: One 50 m maximal-effort freestyle sprint from wall push-off.
- Recovery: 4-minute inter-set rest.
- Sets or repetitions: 6 repetitions.
- Intensity: Maximal effort.
- Session duration: At least about 53 minutes including 20-minute warm-up, 10-minute rest, sprints, and rest intervals; exact duration not directly reported.
- Frequency: Single testing session.
- Program length: Single session.
- Progression: No longitudinal progression; analyzed by sprint order 1-6.

## Outcomes

### SSIT physiological and perceptual load
Status: mixed
During 6 x 50 m SSIT, mean velocity was 1.63 +/- 0.12 m/s, blood lactate was 12.15 +/- 1.48 mmol/L, RPE was 14.7 +/- 1.61, stroke rate was 44.11 +/- 2.86 cycles/min, and stroke length was 1.12 +/- 0.11 cycle/m. Lactate and RPE increased across the session.

Descriptive Table 1 values; no intervention p-values reported for these means.

### 100 m freestyle performance reference
Status: unclear
Mean 100 m velocity was 1.68 +/- 0.11 m/s, blood lactate was 12.97 +/- 1.86 mmol/L, and RPE was 15.81 +/- 1.72.

Descriptive Table 1 values.

### Network topology
Status: mixed
Across sprint orders 1-6, networks showed stable high-density, low-modularity structure linking SSIT and 100 m freestyle variables.

Network density ranged from 0.426 to 0.492; modularity ranged from 0.198 to 0.243; number of nodes was 16 or 17 and edges 56-61.

### Centrality of velocity, lactate, and RPE
Status: improved
Degree and eigenvector centrality for SSIT velocity, blood lactate, and RPE increased as sprint repetitions progressed, positioning them as central hubs in relation to 100 m freestyle performance.

Centrality trends reported from Fig. 5; exact numeric centrality values not provided in extracted text.

### Centrality of stroke variables
Status: mixed
Stroke rate centrality declined, while stroke length influence remained relatively stable; the fourth 50 m may represent a turning point in technical parameters.

Centrality trends reported from Fig. 5 and discussion; exact numeric values not provided in extracted text.

## Practical Insights

- This is athlete-performance evidence, not general consumer HIIT evidence.
- In repeated maximal sprint intervals, later repetitions may reveal rising metabolic and perceptual load while technical variables shift under fatigue.
- For app translation, pace/velocity and RPE are more practical monitoring signals than blood lactate or network centrality.

## Limitations

- Small sample of 16 adolescent swimmers
- Highly trained and sport-specific population
- Cross-sectional single-session design
- No control group and no long-term training adaptation
- Freestyle swimming only
- Complex network analysis is exploratory and does not infer causality

## Safety And Adherence

- No adverse events or injuries were reported in the extracted full text.
- Participants were screened for good health and absence of recent cardiopulmonary disease or musculoskeletal injury.
- Tests were separated by 48 hours and preceded by standardized warm-up and rest.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41555447/) (pubmed)
- [DOI](https://doi.org/10.1186/s13102-025-01515-6) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12908288/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.